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Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0656Z Mar 24, 2019)
 
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Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
256 AM EDT Sun Mar 24 2019

Valid Mar 24/0000 UTC thru Mar 27/1200 UTC

...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...

00Z Model Evaluation With Preferences/Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Plains closed Low shearing into Ohio Valley early Mon across
Southeast Tues
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend
Confidence: Above average

07z update: No major differences noted with the rest of the 00z
guidance now available. The preference for a non-NAM solution
still looks good.

---previous discussion---
Current mid/upper level closed low over the central Plains is
initialized well by the current suite of model guidance. As the
feature opens/weakens in the next 24-48 hours over the lower OH
Valley, the latest guidance has it pushing as an open wave across
the Carolinas Monday night. The NAM remains the furthest
south/southwest with this feature as it digs across the Southeast
US, though the 12z UKMET shows somewhat similar look. The
CMC/ECMWF/GFS all have similar solutions, bringing the axis of the
wave across the central Carolinas by 06z on the 26th. Overall, a
blend incorporating most of the guidance except the NAM should
suffice for the mass fields with this feature. 


Shortwave moving through the Great Basin/C Plains to Southeast
Sun-late Tues
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 00z GFS/NAM/CMC/UKMET blend
Confidence: Slightly below average

07z update: The 12z ECMWF trended more amplified with the
shortwave crossing through the Southeast US, even closing off over
northern FL by early Wednesday morning. This is different from the
rest of the operational 00z model guidance and also is not
represented much by the ensemble guidance. The 00z CMC and 00z
UKMET have more similarities with the GFS and NAM, so for now,
will show a preference for a non-ECMWF blend, especially toward
the end of the forecast period. 

---previous discussion---
A piece of energy breaking off the large gyre off the west coast
will rotate through portions of the central Rockies through
tonight into Sunday before crossing the central Plains and
eventually portions of the Southeast US by mid-week. There is not
a lot of phasing with this feature and the lagging shortwave
discussed above, but the two do work to keep troughing in place
across the Southeast US and mid-Atlantic region. Here the trough
should push further south, reaching northern Florida by Tuesday
night. The NAM is now more similar to the 12z ECMWF while the GFS
is not as deep (weaker) but not nearly as much as the CMC (which
is slower and weak).


Large Pacific Gyre's First Wave Entering Northwest Monday;
Main Core Nearing Northern CA by Late Tuesday
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend (weighted toward 00z GFS/ECMWF)
Confidence: Average

07z update: It seems like the 00z ECMWF/CMC/UKMET want to hold
back the main gyre from moving onshore about 6-12 hours later than
what the GFS and to some degree the NAM advertise. Though, the
differences are relatively minor and the sensible weather impacts
are probably similar. The first piece of energy moving into the
Pacific Northwest has fairly good agreement as well. So for now
the preference for a general model blend with some weight given to
the ECMWF/GFS to wash out their biases seem reasonable at this
point.

---previous discussion---
GOES-W WV imagery shows compact closed low around 49N, 149W
currently and this large gyre will slowly advance eastward toward
the western US coast through the forecast period. Pieces of energy
will break off and move onshore but the main core of the system
will likely brush the western US coast late Tuesday or Wednesday.
The first piece of energy arrives Monday across the Pacific
Northwest and for the most part, the latest model guidance is in
reasonable agreement with this feature as it hugs the coastline
then moves into southern British Columbia. Outside of the UKMET,
the timing and orientation of the upper level pattern is fairly
similar, while the UKMET is slower and also slightly more
amplified with its axis.


Model trends at www.wpc.noaa.gov/html/model2.html
500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml

Taylor